Statistical Analysis
All statistical analyses were performed with SPSS v.23.0 (IBM Corp.,
Armonk, NY, USA). Associations between nominal variables were examined
using χ2 test and Fisher’s exact test. Associations
between continuous and quantitative variables were examined using
Mann-Whitney U-Test. Potential confounding variables were assessed by
Cox proportional hazards regression model. A two-sided p-value of
<.05 was considered statistically significant for all
analyses.